Heaters for the rapid thermal processing of semiconductor substrates during the manufacture of integrated circuits are known in the art. Such heaters are used for annealing, heating and other purposes during the manufacture of integrated circuits. Some conventional heaters are composed of a flat array of heating elements, such as halogen heat lamps. The combination of multiple heating elements electrically wired together is sufficient to provide the required amount of heat for wafer processing. However, with this type of heater, it is difficult to control the heat energy distribution falling on the wafer due to the characteristics of the individual heat lamp elements and their associated reflectors. This poor control of the heat energy distribution results in low power consumption efficiency.
Also known in the art is a heater configuration that uses an array of individual heating elements positioned in hollowed out cylindrical openings in the heater body. Each individual lamp can be considered a point source of heat illuminating a relatively small area of the wafer. This configuration permits greater control over the heat illumination of the wafer. However, this configuration is less efficient than the previous one described due to the large number of multiple reflections which can be responsible for an energy loss in the order of 30%. The multiple reflections are generated because the heat lamp is mounted inside a cylindrical cavity. Although the interior surface is a polished reflector, the geometry of the cylinder is such that a significant amount of the heat is not reflected directly out of the opening. Multiple reflections, besides being wasteful, cause unnecessary additional heating of the filament, reducing the life of the heat lamp, decreasing the efficiency of the heater, increasing the number of heat elements required and consequently the electrical power required. In addition, the machining required to form the cavities in the heater body is complex and expensive. Also, the angular energy distribution of such a heater is non homogeneous due to the geometrical restrictions of each socketed or cavity reflector.